SPITZER SPACE TELESCOPE MEASUREMENTS OF DUST REVERBERATION LAGS IN THE SEYFERT 1 GALAXY NGC 6418

We present results from a 15 month campaign of high-cadence (∼3 days) mid-infrared Spitzer and optical (B and V) monitoring of the Seyfert 1 galaxy NGC 6418, with the objective of determining the characteristic size of the dusty torus in this active galactic nucleus (AGN). We find that the 3.6 and 4...

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Detalles Bibliográficos
Autores: Vazquez, Billy, Galianni, Pasquale, Richmond, Michael, Robinson, Andrew, Axon, David J., Horne, Keith, Almeyda, Triana, Fausnaugh, Michael, Peterson, Bradley M., Bottorff, Mark, Gallimore, Jack, Eltizur, Moshe, Netzer, Hagai, Storchi-Bergmann, Thaisa, Marconi, Alessandro, Capetti, Alessandro, Batcheldor, Dan, Buchanan, Catherine, Stirpe, Giovanna, Kishimoto, Makoto, Packham, Christopher, Pérez Jiménez, Enrique, Tadhunter, Clive, Upton, John, Estrada-Carpenter, Vicente
Tipo de recurso: artículo
Estado:Versión aceptada para publicación
Fecha de publicación:2015
País:España
Institución:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/397507
Acceso en línea:http://hdl.handle.net/10261/397507
Access Level:acceso abierto
Palabra clave:Galaxies: activegalaxies: active
Galaxies: individual (NGC 6418)
Galaxies: nuclei
Galaxies: Seyfert
Descripción
Sumario:We present results from a 15 month campaign of high-cadence (∼3 days) mid-infrared Spitzer and optical (B and V) monitoring of the Seyfert 1 galaxy NGC 6418, with the objective of determining the characteristic size of the dusty torus in this active galactic nucleus (AGN). We find that the 3.6 and 4.5 μm flux variations lag behind those of the optical continuum by days and days, respectively. We report a cross-correlation time lag between the 4.5 and 3.6 μm flux of days. The lags indicate that the dust emitting at 3.6 and 4.5 μm is located at a distance light-month () from the source of the AGN UV-optical continuum. The reverberation radii are consistent with the inferred lower limit to the sublimation radius for pure graphite grains at 1800 K, but smaller by a factor of ∼2 than the corresponding lower limit for silicate grains; this is similar to what has been found for near-infrared (K-band) lags in other AGNs. The 3.6 and 4.5 μm reverberation radii fall above the K-band size-luminosity relationship by factors and , respectively, while the 4.5 μm reverberation radius is only 27% larger than the 3.6 μm radius. This is broadly consistent with clumpy torus models, in which individual optically thick clouds emit strongly over a broad wavelength range. © 2015. The American Astronomical Society. All rights reserved.

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